1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) panel module which integrates various components such as an LCD panel, and an LCD device including the LCD panel module.
2. Description of the Related Art
An LCD device includes features of a thin shape, a light-weight, and low power consumption. Thus, an LCD device is widely used such as in office automation (OA) equipment, audio video (AV) equipment, portable terminal equipment or the like.
Generally, an LCD device includes a backlight, an optical member, an LCD panel, and a chassis for holding and attaching these members as main components in a broad sense.
More specifically, the backlight includes a plurality of parts, such as a lamp, a base for supporting the lamp, a reflecting plate and the like. The optical member includes a plurality of parts, such as a diffusing plate, an optical sheet and the like, which adjust a light of the backlight to be a uniform illumination light. A liquid crystal (LC) layer is sandwiched between two opposing substrates in the LCD panel.
As above described, the LCD device includes many parts. Therefore, it is troublesome to treat the many parts in a manufacturing process. Then, a related art is proposed to combine a number of the parts and make several units in order to decrease the number of the parts to be treated in the manufacturing process of a liquid crystal display.
FIG. 20 is an exploded view of a backlight unit of an LCD device, as a related art. In FIG. 20, parts such as a lamp 95, a lamp support base 94, and a reflecting plate 96, constitute so-called a backlight. Further the backlight, a diffusing plate 93, an optical sheet 92 and a backlight chassis 91 for fixing the above-mentioned parts constitute a backlight unit 90.
FIG. 19 is a perspective view showing a configuration of an LCD device as a related art. The LCD device shown in FIG. 19 includes an LCD panel 80, the backlight unit 90 to which is referred in FIG. 20, and a front chassis 70 for attaching the LCD panel 80 and the backlight unit 90. Here, a printed wiring board 81 is connected to an edge part of the LCD panel 80 via a TCP (Tape Carrier Package) 82.
In the LCD device having such structures, the number of the parts to be treated in a manufacturing process may be reduced. Japanese Patent Application Laid-Open No. 2002-311418 discloses such LCD device.
An LCD panel requires a driver integrated circuit (IC) which drives the LCD panel, and circuit elements such as a printed wiring board which perform signal processing. Generally, as a structure that mounts circuit elements in the LCD panel, Chip On Glass (COG), Chip On Board (COB), Tape Carrier Package (TCP) and Chip On Film (COF) are known.
More specifically, in COG and COB, the circuit elements are directly mounted on a substrate of the LCD panel. On the other hand, in TCP and COF, circuit elements are connected to the substrate using wiring lines in a flexible film (hereafter, flexible substrate). However, in the LCD device, a width of an edge portion (rim) in a screen of an LCD panel (i.e. a width of a front chassis frame) is generally required to be narrow.
As a related art, FIG. 21 is a perspective view showing a configuration of an LCD device disclosed by Japanese Patent Application Laid-Open No. 1998-148819. Generally, when circuit elements are connected by using a TCP or a COF, a structure as shown in FIG. 21 is utilized. More specifically, in FIG. 21, a flexible substrate 3 is extended along a side of an LCD device and is connected to a printed wiring board 5 arranged on a rear side of a backlight unit (refer to pages 5-6 and FIG. 4 of Japanese Patent Application Laid-Open No. 1998-148819). Further, in FIG. 21, a liquid crystal cell 1, a frame 2 and integrated circuits 7 are housed in a bezel 11.
However, the LCD device in which the LCD panel and the backlight unit above-mentioned are separated have some difficulties described below.
That is, in the LCD device mentioned above, the LCD panel is placed on the backlight unit. A printed wiring board connected to the LCD panel is usually mounted, by using screws or the like, on a rear face of the backlight unit. In the LCD device having such structure, when the LCD panel and circuit elements are transported and when repairing such as an exchange of a backlight unit or a lamp is performed, it is necessary to place the printed wiring board on the rear face of the backlight and perform grounding during assembling.
Therefore, in the LCD device having the structure mentioned above, following difficulties occur:
(1) a connection defect may occur due to a troublesome grounding work;
(2) damage of an LCD panel and/or a circuit board may occur due to an excessive load in a transportation or an assembling process;
(3) contamination or damage of an LCD panel may occur due to a dust in a transportation or an assembling process.
Hereinafter, the difficulties will be described in detail.
First, grounding of a printed wiring board is difficult. That is, an LCD device tends to be influenced by an external electromagnetic field. When an electromagnetic noise superposes on the printed wiring board, it causes defects such as a malfunction of the LCD device and an abnormal display thereof. Therefore, it is desirable that an electric potential of a grounding electrode of the printed wiring board is the same as that of various chassis such as the front chassis and the backlight chassis.
For this reason, the chassis (the front chassis 70 and the backlight chassis 91 in an example shown in FIG. 19 and FIG. 20) outside the LCD device and a printed wiring board has to be electrically connected for a stable grounding.
Accordingly, after the printed wiring board is fixed on the rear face of the backlight unit, a grounding terminal of the printed wiring board is connected to a chassis of the backlight unit with a wiring.
In addition, the work for grounding of the printed wiring board is generally performed during assembling processes. After the printed wiring board is disconnected during exchange of a lamp installed in the backlight unit, an assembling operator or a maintenance engineer have to restore the grounding of the printed wiring board. As a result, an assembly process and a maintenance work become troublesome in connecting configuration above-mentioned. When the work for grounding is carelessly incomplete, an electromagnetic noise cannot be blocked off certainly.
Secondly, the circuit elements such as a driver IC, a flexible substrate and a printed wiring board, and an LCD panel tend to be damaged. That is, in the above-mentioned TCP and COF, an LCD panel is frequently transported as a part of the LCD device and at the time, the circuit elements arranged around the LCD panel is not amounted thereto during transportation. Therefore, since the circuit elements touch other members during transportation, excessive load may be applied on the circuit elements or the members.
A lamp for a backlight unit is a part with the shortest life-span in parts included in an LCD device. Thus, while the LCD device is working, the lamp may be exchanged. When a lamp is taken out of the backlight unit for an exchange thereof, a printed wiring board fixed on the rear face of the backlight unit is disconnected and, an LCD panel and a backlight are separated. After that, in order to exchange the lamp, the backlight unit has to be taken apart. After an exchange of the lamp, the backlight unit and the LCD panel are combined again, and then the printed wiring board is fixed on the rear face of the backlight unit. During the exchange work, the circuit elements may receive excessive load from handling by an assembly operator and a maintenance engineer and may be damaged.
In the above-mentioned case, the LCD panel by itself is transported in a factory process and between factories. Thus, the interference (i.e. contact) with other members in the LCD panel during transportation may cause damage, bend or the like in the LCD panel. In particular, when the size of LCD panel is larger, a weight and the interference thereof increase. Since transformation and/or distortion tend to occur during transportation of such large LCD panel, the risk of damage such as a warp and a breakage therein may be increased. When an LCD panel and a backlight unit are assembled in a destination for final assembly, damages may be given to the LCD panel.
Thirdly, an LCD panel may be contaminated by dusts, and an exposed surface thereof may get damaged.
That is, an LCD panel itself is usually manufactured in a clean environment, a so-called clean room. However, even if the LCD panel is manufactured by the clean environment, during transportation for LCD device assembly, assembly of a backlight unit or, lamp exchange work, dusts may adhere on the LCD panel. In such case, an operator may damage the LCD panel by mistake.
In an LCD device, various kinds of light sources, such as a cold cathode fluorescent lamp (hereinafter, referred to as “CCFL”), an external electrode fluorescent lamp (hereinafter, referred to as “EEFL”) a light-emitting diode (hereinafter, referred to as “LED”) or the like are available for a backlight. It is desirable for manufacturers who are supplied an LCD panels to be able to choose a desired kind of backlight in accordance with their several use. An LCD panel module and an LCD device in which a backlight can be readily exchanged are desired under such background.